1. Field of the Invention
The present invention relates generally to a system for plasma treating a plastic component.
2. Background Art
Plastic components commonly have appearance and durability requirements depending on their application. For example, a plastic trim component, such as a bumper fascia or an instrument panel, may be decorated with a paint and have both distinctness of image (DOI) and paint adhesion requirements. DOI is an objective appearance criterion for brilliance and gloss which includes the visual effects from a rough or bumpy coating surface, sometimes referred to as “orange peel.” DOI may be measured, for example, with a BYK-Gardner wave-scan unit. Both paint adhesion and DOI are dependent on the interfacial surface chemistries between the plastic component and the paint.
Factors influencing the surface chemistry of a plastic component may include the type of plastic used, contamination on the surface prior to coating, and the presence of mold release agents. The surface chemistry is also subject to scratch, slip or process additive packages which may effectively lower the surface's coefficient of friction. These factors contribute to the overall surface energy of the plastic. Moreover, a lower surface energy plastic may be more difficult to coat, due in part to poor wet-out of the surface by the coating, which may result in “orange peel” and a lack of paint adhesion.
In order to overcome these factors, the plastic surface may be prepped prior to coating or a more elaborate painting process may be employed. For example, a multi-step aqueous acid or base chemical wash process with flashing ovens may be used to remove mold release agents and contaminates. Alternatively, a plastic system with an aggressive solvent package may be used to initially swell the plastic surface, thus, allowing for polymer entanglement between the plastic and the paint. Also, a chlorinated polyolefin adhesion promoter (ad pro) may be used as a surface prep prior to applying a decorative paint. However, the use of aggressive solvents or chlorinated polyolefin adhesion promoters is often undesirable for both economic and environmental reasons.
More recently, vacuum plasma treatment has been used to increase the surface energy of plastic components prior to painting. This method often eliminates or minimizes the need for further surface preparation or for a more elaborate painting process. However, this methodology may require major expenditures for equipment, including vacuum chambers which command a less efficient batch processing approach.
There is a need for a methodology and a system for treating and coating a plastic component which may avoid some of these undesirable results.